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What is diarrhea?

Diarrhea occurs when one passes loose or liquid stools more frequently than normal. Typically, three or more of these passages per day is considered diarrhea.1

Diarrhea has been a major health problem throughout history, affecting mostly children and the elderly. It remains a significant cause of disease and death worldwide.2 In the U.S. in 2003, the estimated prevalence was 3-7% in adults, and 8% in children 5 years old or younger. 83% of deaths from acute diarrhea occur in elderly patients.3

What are common symptoms?

Acute diarrhea lasts less than two weeks. Chronic diarrhea lasts longer, and may involve more severe diseases. The most common symptoms of infectious diarrhea are (in order of frequency)1,4:

  • Loose or liquid stool
  • Abdominal pain
  • Vomiting
  • Bloating
  • Nausea
  • Fever
  • Bloody stool

What are the causes?

Infectious agents – such as parasites, bacteria, and viruses – are the most common cause of diarrhea. Parasites can cause severe chronic diarrhea, while diarrhea caused by bacterial infections usually lasts one week or less.

Common bacterial causes of acute diarrhea are enterotoxigenic, including Campylobacter, Escherichia coli, Shigella, Salmonella, and Vibrio parahaemolyticus.1 In industrialized regions, Clostridium difficile has been related to recurrent diarrhea after antibiotic use, particularly among hospitalized patients. Noroviruses are common viral causes of infectious diarrhea.

Other, non-infectious causes of diarrhea include rare genetic mutations in intestinal proteins, and inflammation as a consequence of autoimmune diseases, such as irritable bowel disease and celiac disease.2

The main risk factors for diarrhea are5:

  • Antibiotic use
  • Consumption of food associated with foodborne illness
  • Fecal-oral contact
  • Immunosuppression
  • Infectious exposures (i.e. daycares)
  • Poor access to appropriate care
  • Poor hygiene
  • Poverty
  • Pre-existing intestinal infections
  • Travelling to developing countries
  • Undernutrition
produce enterotoxins that affect the intestines, generating effects similar to food poisoning.

How does this topic relate to my microbiome?

A patient with diarrhea has a disrupted gut environment, in which diarrhea-causing agents overgrow. This further disturbs the balance and normal functioning of the gut microbiota.6 Several studies have shown that C. difficile causes a decrease in the number of Bacteroides and Firmicutes in the gut of patients with diarrhea compared to healthy individuals.7 Certain probiotics can restore the gut microbiota in patients with recurring diarrhea and other intestinal diseases.4,8

Which diseases/topics are related to diarrhea?

Conditions related to diarrhea are3,4,5

  • Celiac disease
  • Food intolerance
  • Food poisoning
  • Gastroenteritis
  • Inflammatory bowel disease
  • Irritable bowel syndrome

Immunocompromised patients are susceptible to less common gastrointestinal pathogens. Diarrhea resulting from these pathogens is a major cause of death for HIV-infected patients. Even non-fatal chronic diarrhea can greatly reduce quality of life.9

How can people take action?

For correct examination and treatment, consult your healthcare provider, since some cases of diarrhea require prescription medication. Due to the large volume of liquid lost during diarrhea, the first treatment for patients is often rehydration.10 Drinking solutions containing water, salt, and sugar – such as diluted fruit juices, broths, or soups – is recommended. Adequate nutrition can also help restore normal functioning in the intestine. Boiled food with salt is preferable, while dairy products (except yogurt) and foods with a high fat content should be avoided.11 Probiotics can prevent and reduce the duration of infectious diarrhea.4,12


1. Dupont, H. L. (2016). Persistent diarrhea a clinical review. JAMA – Journal of the American Medical Association, 315(24), 2712–2723.

2. Thiagarajah, J. R., Donowitz, M., & Verkman, A. S. (2015). Secretory diarrhoea: Mechanisms and emerging therapies. Nature Reviews Gastroenterology and Hepatology, 12(8), 446–457.

3. DuPont, H. L. (2014). Acute Infectious Diarrhea in Immunocompetent Adults. New England Journal of Medicine, 370(16), 1532–1540.

4. Guarino, A., & Guandalini, S. (2015). Probiotics for Prevention and Treatment of Diarrhea. J.Clin.Gastroenterol., 45(December), S37–S45.

5. Das, J. K., & Bhutta, Z. A. (2016). Global challenges in acute diarrhea. Current Opinion in Gastroenterology, 32(1).

6. Balamurugan, R., Janardhan, H. P., George, S., Raghava, M. V., Muliyil, J., & Ramakrishna, B. S. (2008). Molecular studies of fecal anaerobic commensal bacteria in acute diarrhea in children. Journal of Pediatric Gastroenterology and Nutrition, 46(5), 514–519.

7. Chang, J. Y., Antonopoulos, D. A., Kalra, A., Tonelli, A., Khalife, W. T., Schmidt, T. M., & Young, V. B. (2008). Decreased Diversity of the Fecal Microbiome in Recurrent Clostridium difficile –Associated Diarrhea. The Journal of Infectious Diseases, 197(3), 435–438.

8. Gareau, M. G., Sherman, P. M., & Walker, W. A. (2010). Probiotics and the gut microbiota in intestinal health and disease. Nature Reviews Gastroenterology & Hepatology, 7(9), 503–514.

9. Siddiqui, U., Bini, E. J., Chandarana, K., Leong, J., Ramsetty, S., Schiliro, D., & Poles, M. (2007). Prevalence and Impact of Diarrhea on Health-related Quality of Life in HIV-infected Patients in the Era of Highly Active Antiretroviral Therapy. Journal of Clinical Gastroenterology, 41(5), 484–490.

10. Riddle, M. S., Dupont, H. L., & Connor, B. A. (2016). ACG clinical guideline: Diagnosis, treatment, and prevention of acute diarrheal infections in adults. American Journal of Gastroenterology, 111(5), 602–622.

11. Duggan, C., Santosham, M., & Glass, R. I. (1992). The management of acute diarrhea in children: oral rehydration, maintenance, and nutritional therapy. Centers for Disease Control and Prevention. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports, 41(RR-16), 1–20.

12. McFarland, L. V. (2007). Meta-analysis of probiotics for the prevention of traveler’s diarrhea. Travel Medicine and Infectious Disease, 5(2), 97–105.